Cardiovascular catheter with laterally stable basket-shaped electrode array

ABSTRACT

An electrophysiological mapping device includes an outer catheter, an inner catheter slidable within the outer catheter, and an electronic activation and recording device for electrically activating electrodes on the inner catheter and/or recording electric signals received by the electrodes. The distal end of the inner catheter comprises a plurality of arms that carry electrodes. The arms bow outwardly upon extension of the inner catheter from the outer catheter to form a three-dimensional shape. Each arm has a spine of a superelastic material. Each spine is semi-circular in section, and is disposed within a portion of a flexible sheath, the electrode lead wires being disposed in the rest of the sheath. The electrodes are formed from the ends of the insulated electrode lead wires which pass through the sheath, are wrapped around the sheath and then stripped of their insulation. The proximal and distal ends of the spines are fixed to proximal and distal fittings, each having a polygonal segment having flat sides which engage the flat surfaces of the spines and a clamping ring to secure the spines to the segments.

FIELD OF THE INVENTION

The present invention relates to cardiovascular catheters and, inparticular, to such catheters having a retractable basket-shapedelectrode array formed by a plurality of arms, each arm supporting aplurality of spaced-apart electrodes.

BACKGROUND OF THE INVENTION

Electrophysiology is a specialty within the field of cardiology fordiagnosis and treatment of electrical abnormalities of the heart.Diagnosis is performed using electrode-bearing catheters placed withinthe heart chambers. Electrodes are positioned along a catheter shaft ina primarily two-dimensional array, although electrode elements spacedlaterally around the catheter shaft give the array a very limited thirddimension. Understandably, this third dimension is limited because ofthe small catheter shaft diameter required for such catheters as theyare introduced into the heart via the veins and arteries of the body.

Electrical abnormalities are typically diagnosed by detecting the courseof electrical activation paths along the endocardial surfaces of theheart chambers over time. To do this, the cardiologist may place severalcatheters within one or more chambers of the heart to get a better"picture" of this electrical activity. Sometimes this electricalactivity is cyclical, i.e., repeats fairly well from heartbeat toheartbeat. In such cases, one catheter may serve to perform thediagnosis by moving the electrodes to various regions and thenpoint-by-point comparing activation times with a reference. Thisreference may be the external EKG or another electrode cathetermaintained in a stable position within a heart chamber.

However, certain types of electrical activity within a heart chamber arenot cyclical. Examples include arterial flutter or arterialfibrillation, and ventricular tachycardia originating in scars in thewall of the ventricle that have resulted from infarcts. Such electricalactivity is random from beat to beat. To analyze or "map" this type ofelectrical activity, the "picture" must be obtained during one beat. Inother words, all the points of the map or picture must be obtainedsimultaneously within one-tenth of a second.

One solution to improve mapping is disclosed in U.S. Pat. Nos. 4,522,212to Gelinas et al. and 4,699,147 to Chilson et al. In these patents, acatheter has, at its distal end, multiple lead-carrying arms whichextend in a three-dimensional array, each arm having an inner centralrib and electrodes spaced along its length. In Chilson et al., the armsare fixed at their distal end, but free to move within an outer cathetertube at their proximal end. The lead-carrying arms may be retracted intoand extended from the outer catheter tube. The distal end of thecatheter is directed to the designated areas of the heart and withdrawn,with the lead-carrying arms retracted within the outer catheter tube.Once at the designated areas, the arms are extended from the outercatheter tube to form a three-dimensional shape, referred to as an"elliptical envelope."

The catheter described in Chilson et al. is able to hold a large numberof electrodes in different relative positions within a heart chamber. Bythis means, the cardiologist can obtain a map of electrical activity inone heartbeat by recording electrical signals from all the electrodessimultaneously. This is done by analyzing the spatial and temporalrelationship of the electrical signals received at the electrodes.

By rotating the catheter and/or moving it longitudinally and recordingelectrical signals, a series of maps or pictures can be produced. Aseries of such pictures provides a "moving" picture of successiveheartbeats, which may be able to better define the ectopic sites ofactivation or other activation pathways that contribute to themalfunction. This type of information may then allow the cardiologist tointervene with another catheter to destroy that causative tissue. Suchdestruction of heart tissue is referred to as "ablation," which is arapidly growing field within electrophysiology and obviates the need formaximally invasive open heart surgery.

In Chilson et al. the arms are easily moved relative to each other andhence, the shape of the elliptical envelope varies from time to time andmay vary even when positioned in one place due to the pumping heartchamber or the effect of rotation. Accordingly, the spatial relationshipof the electrodes is subject to variation of unknown amounts. This, inturn, imparts a high degree of uncertainty or error in any map ofelectrical activity produced with the use of this catheter.

SUMMARY OF THE INVENTION

The present invention provides an electrophysiological mapping cathetercomprising an outer catheter and an inner catheter. The inner cathetercomprises a tubular shaft extending longitudinally through the outercatheter tube. At the distal end of the shaft, there is a plurality offlexible arms, each arm carrying a plurality of spaced-apart electrodes.The flexible arms of the basket are fixed at their proximal ends to aproximal fitting and fixed at their distal ends to a distal fitting. Theshaft is movable longitudinally within the outer catheter and the armsand electrodes can be retracted into and extended from the outercatheter tube. When the arms are extended out of the catheter tube, thearms flex outwardly to form a "basket", the electrodes forming athree-dimensional array.

Each arm comprises a reinforcing spine surrounded by a tubular flexiblesheath having a generally circular cross-section. Each reinforcing spinepreferably has a semi-circular cross-section with the flat surface ofthe spine facing inwardly, i.e. toward the axis of the catheter. Thespines preferably lie in the outwardly facing portion of the tubularsheath with the remainder of the tubular sheath filled by insulatedelectrode lead wires.

The electrodes are preferably formed on the arms by passing insulatedlead wires through the wall of the tubular sheath, wrapping the wiresaround the tubular sheath and gluing it thereto. The insulation is thenstripped off the outer surfaces of the lead wires which are wrappedaround the sheath. The electrode lead wires extend from the arms throughthe proximal fitting and through the lumen of the inner catheter shaftto a stimulation and/or recording device.

The proximal and distal fittings include polygonal rod segments whoseflat sides correspond in number to the number of spines and engage theflat surfaces of the spines. A clamping ring is positioned around thespines to hold them in proper orientation on the polygonal rod segment.In a preferred embodiment, the spines are formed out of a superelasticmaterial, particularly a nickel-titanium alloy, with "shape memory."Such material returns to its bowed shape upon extension of the arms outof the outer catheter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged view of the distal end of an inner and an outercatheter with the inner catheter extended from the outer catheter, thusforming a basket of electrodes at the distal end of the inner catheter;

FIG. 2 is an enlarged view of an electrode pair from the circled portionlabeled "2" in FIG. 1;

FIG. 3 is a longitudinal cross-sectional view of the distal end of theinner catheter shaft;

FIG. 4 is an enlarged transverse sectional view taken along line 4--4 ofFIG. 1 and showing one arm of the basket of FIG. 1;

FIG. 5 is a transverse sectional view of a proximal fitting which hasbeen taken along line 5--5 of FIG. 1;

FIG. 6 is a transverse sectional view of a distal fitting of the basketof FIG. 1 taken along line 6--6 of FIG. 1;

FIG. 7 is a schematic view of the ten assymetric positions of rotation;and

FIG. 8 is a partial perspective and partial schematic view of anelectrophysiological mapping system according to the invention,including an inner catheter, an outer catheter, and an activation andrecording device, showing the inner catheter retracted within the outercatheter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIGS. 1-7, a preferred electrophysiological mappingsystem is shown. The system includes an electronic stimulation and/orrecording device, an inner catheter 6, and an outer catheter tube 8.Outer catheter tube 8 carries inner catheter 6 to a mapping site, e.g.,within a heart chamber, and also serves to withdraw the inner catheter 6from the mapping site. Inner catheter 6 is slidable longitudinallywithin outer catheter tube 8. A hemostasis valve, not shown, is providedat the proximal end of the outer catheter tube to prevent backflow ofblood through the lumen of the outer catheter tube 8. FIG. 8 shows themapping system, including electronic stimulation and/or recording device4, and inner catheter 6 retracted within outer catheter tube 8.

Inner catheter 6 comprises an elongated, tubular catheter shaft 7 andfive electrode carrying arms 9 at the distal end of the catheter shaft7. Inner catheter 6 can be moved relative to outer catheter tube 8between an extended position as shown in FIG. 1 wherein arms 9 extendcompletely out of the distal end of outer catheter tube 8 and aretracted position generally as shown in FIG. 8 wherein the arms 9 areretracted within the outer catheter tube 8. In the extended position,the arms 9 bow outwardly to define a "basket" structure.

Each arm 9 has its own spaced set of ten electrodes 11, shown herein asfive hi-polar electrode pairs. In the embodiment shown, the fiveelectrode pairs are generally evenly spaced. It is understood, however,that the number and spacing of the electrodes may vary as desired.Further, single electrodes may be used rather than bipolar electrodepairs.

The arms 9 are fixed at their proximal ends to a proximal fitting 12,and also fixed at their distal ends to a distal fitting 14. Proximalfitting 12 is, in turn, fixed to the distal end of the catheter shaft 7.The catheter shaft 7 comprises a central lumen 13 which extends from itsproximal end to its distal end. The shaft 7 preferably comprises atubular wall 10 of high-strength braided stainless steel or otherhigh-strength wire or fiber, sandwiched between inner and outer layersof firm, yet flexible, polyurethane, for example, as disclosed in U.S.patent application Ser. No. 07/645,230, filed Jan. 24, 1991,incorporated by reference herein. This high-torque shaft structureallows a physician to control the orientation of the electrode basketwithin the heart chamber by rotating the catheter shaft 7 where itenters the patient's body, which is usually at the groin or neck. Theshaft 7 preferably further comprises a nylon stiffening sleeve 15 liningthe interior of the tubular wall 10.

FIG. 4 is a sectional view of an arm 9. The arm 9 has an outer tube 18of a flexible insulating material, e.g., a plastic such as flexiblepolyurethane tubing. Inside the plastic tubing are the plurality ofelectrode lead wires 20, each wire having an insulation coating and acentral conductive wire core. The wires 20 extend from the electrodes 11through the plastic tubing 18 of the arms 9, through the proximalfitting 12 and lumen of the shaft 7 to the stimulation and/or recordingdevice 4. In this embodiment, there are fifty lead wires 20 whichcorrespond to the ten electrodes 11 carried on each of the five arms 9.The number of electrodes and, hence, electrode lead wires may be variedas needed.

The lead wires 20 are separated into five bundles 22, each bundle 22containing the ten lead wires 20 which correspond to the ten electrodes11 carried by each particular arm 9. At their proximal ends, theseparate wire bundles 22 terminate in separate plug connectors 24, whichare plugged into the activation and recording device 4. The total numberof lead wires 20 in each bundle 22 is equal to the number electrodes 11on each corresponding arm. Therefore, if there are 5 electrodes on eacharm, there will be 5 leads in the corresponding bundle. If there are 5electrode pairs, there will be 10 electrode leads in the bundle. Eachbundle 22 of leads is contained in an insulated flexible tube, which inturn enters the plug connector.

With reference to FIG. 2, each electrode 11 is formed by passing a leadwire 20 through the outer tube 18 of the arm 9. The wire 20 is wrappedtightly around the tubing 18 and glued and then the insulation coatingfrom the outwardly facing surfaces of the lead wires, i.e. the surfaceswhich will contact the heart wall, is stripped to expose the metal ofthe lead wire.

It is preferable that the electrode lead wires 20 be of a metal which isinert in blood. MONEL 400, which is a trademark of Huntington AlloyProducts Division of International Nickel Co., Inc., Huntington, W. Va.,is presently preferred. MONEL refers to a group of corrosion-resistantalloys of predominantly nickel and copper and very small percentages ofcarbon, manganese, iron, sulfur, and silicon. Some such alloys alsocontain a small percentage of aluminum, titanium, and cobalt. MONEL 400has the additional benefit that it is not as easily visible underfluoroscopic x-ray as platinum. Therefore, the electrodes can be smalland all of equal size and uniformly arranged.

With materials which are more radiopique, even spacing of the electrodesis not desirable because it is difficult to distringuish which arm is atwhich location. For example, in U.S. Pat. No. 4,699,147 to Chilson etal., the electrodes on one arm are spaced unevenly with respect to theelectrodes on each other arm. If the electrodes were spaced evenly inthe device of Chilson et al., it would be difficult to identify whicharm is which under x-ray. In the preferred embodiment of the presentinvention, the electrode pairs on each arm are able to be spaced evenlywith respect to each other and are located on corresponding positions tothe electrodes on each other arm, although uneven spacing on each armand staggered spacing with respect to the electrodes on other arms isacceptable.

The even spacing of electrodes would normally result in difficultydetermining which arm is at which location. However, in accordance withone aspect of the invention, markers 38, at different locations alongeach arm, such as in a staggered or spiral pattern, are positioned onthe arms, respectively. These markers preferably are of a material whichis easily identifiable under fluoroscopic x-ray, such as platinum, andare in the shape of a band or ring fixed around each arm.

The arms 9 are supported by a flexible rib or spine 25 having asemi-circular cross-section. The spine 25 is preferably formed out of asuperelastic material, such as a nickel-titanium alloy having about 54to 57% nickel, preferably 55%, and the remainder is titanium, preferably45%. Such materials exhibit superelasticity. That is, it can be deformedby an external stress, e.g. bent, and, when that stress is removed, itwill return to its original shape. A presently preferred material issold under the trademark NITINOL by U.S. Nitinol of Saratoga, Calif.Such a superelastic spine 25 allows the arms 9 of the basket to beretracted into and extended from the outer catheter tube 8 and otherwisesubjected to bending, such as from the beating heart chamber, yet stillreturn to its proper shape, even if extremely deformed.

The spine 25 preferably has an insulation coating, e.g., of polyurethanepaint, to help hold it in place and shield it from the lead wires. Thelead wires 20 and spine 25 are positioned in tube 18 such that the spine25 occupies the outwardly facing portion of the tube 18, while the leadwires 20 occupy the inwardly facing portion of the tube 18. The terms"outwardly" and "inwardly" are relative to an axis or centerline of thebasket. Spines 25 having a semi-circular cross-section are preferredover spines having circular cross-sections of the same cross-sectionalarea because they provide greater lateral stability, yet have sufficientflexibility for opening into the "basket" shape when the inner catheter6 is extended out of and collapsed into outer catheter tube 8.

The positioning of the electrode lead wires 20 in the inward portion ofthe tube 18 places the wires 20 away from the heart wall. This enablesthe wire portion used for the electrodes 11 to pass through the tube 18at a location remote from the heart wall and thereby provide a smootherelectrode surface. The hole in the tube 18 through which the lead wire20 extends and lead wire terminus is preferably covered and secured withan adhesive, e.g., polyurethane, in a position where it will not be incontact with the heart chamber wall.

The metal portion of each spine 25 extends beyond the plastic tubing 18at each end and attaches to the two fittings 12 and 14, as shown indetail in FIGS. 3-6. The proximal fitting 12 is formed by a polygonalrod segment 26 having an axial aperture formed therein. The rod segment26 is preferably metal. The number of sides of the polygonal rod segment26 equal the number of spines 25. The flat surface of each spine 25 ispositioned flat against the side of the polygonal rod segment 26 in thesame orientation as the spines 25 are located in forming the basket.

An outer clamping ring 27, e.g., of metal, holds the spines 25 in placeagainst the sides of the polygonal rod segment 26. An adhesive, such aspolyurethane or epoxy, is preferably used to permanently fix the spines,polygonal rod segment 26 and clamping ring.

The proximal fitting 12 is fixedly mounted within the distal end of theinner catheter shaft 7, e.g., by epoxy, polyurethane or other adhesives.The distal end of the nylon sleeve 15 extends up to and butts againstthe proximal end of the polygonal rod segment 26 and clamping ring 27.The electrode lead wires 20 from each arm 9 pass through the axialaperture in the polygonal rod segment 26 and then through the nylonsleeve 15.

Distal fitting 14 is generally the same as proximal fitting 12, in thatit has a polygonal rod segment 29. The spines 25 are fixed to each side,respectively, of the polygonal rod segment 29 and are secured thereto byan outer clamping ring 30. However, no aperture is needed in segment 29because no lead wires are present at the distal fitting. In addition, itis preferable to provide an outer plastic tip member 31, which isrounded in shape at its distal end, to help the inner catheter slidethrough arteries or veins with minimum trauma and to prevent trauma inthe heart chamber. The tip member 31 may be fixed by using adhesive,e.g., epoxy or polyurethane.

The distal fitting 14 is the same size as or, if desired, may be of asmaller scale than proximal fitting 12. These fittings 12 and 14 holdthe spines 25 in proper angular orientation with respect to each other,and thus maintain the proper spacing of the arms 9 and the properorientation of the basket. This is important because the cardiovascularcatheter is subjected to a pumping heart wall and must also be rotatedduring the electrophysiological mapping process. In addition, the spines25 are subjected to bending and other forces during retraction into theouter catheter and extension therefrom.

The basket is shown with five arms 9, which is the most preferablenumber. As shown in FIG. 7, there are ten asymmetrical positions ofrotation. That is, the arms are arranged so as to define the fivecorners of a pentagon, each corner corresponding to a position ofrotation. Rotation of the basket by 36° provides five additionalpositions of rotation. By the use of five arms, the basket very nearlyappears round in rotation when viewed axially. This feature greatlyfacilitates placement and control within a heart chamber because theheart chambers are not round, but are irregular.

A greater number of arms is not preferred because differentiation ofelectrodes becomes more difficult and the inner catheter is moredifficult to fit within the outer catheter. A lesser number of arms ismore practical in that it is smaller and easier to differentiate theelectrodes, but is not preferred because mapping becomes morecumbersome.

In use, the inner catheter 6 is disposed within the outer catheter 8 forplacement in a vein or artery and then subsequently into a chamber ofthe heart. The outer catheter 8 holds the arms 9 of the basketinternally in a collapsed position so that the entire catheter,consisting of the inner catheter 6 and the outer or guiding catheter 8,can be passed down the vein or artery into the heart chamber. Once thedistal end of the catheters has reached the desired heart chamber in theappropriate position, the outer catheter 8 is withdrawn so that the arms9 flex into their predetermined "basket" position. The electrodes 11contact the walls of the heart chamber in this position. Additionaloutward movement of the arms and pressure against the heart wall can begained by pushing forward on the inner catheter shaft 7 causing thebasket to widen outwardly. When mapping has been completed, the outercatheter can be extended back over the basket to collapse the arms, andthen ultimately be withdrawn with the arms therein.

The inner mapping or basket catheter, as described above, has severaladvantages. For example, fixing the spines of the basket at both theirdistal and proximal ends provides a very laterally stable basket. Thisstability is important to hold the catheter in stabile position within abeating heart chamber.

The fittings which hold the distal and proximal ends of the spinestogether, the flat sides of the spines mating with the flat sides of thepolygon, ensure accurate arrangement of the arms in three dimensions.

The semi-circular cross-section of the spines increases the lateralstiffness in comparison with a round cross-section of equal area,thereby increasing the lateral stability of the basket.

The use of superelastic material, such as NITINOL, for the spine resultsin a basket that can be bent, collapsed, and twisted without appreciablepermanent deformation. It is thus highly resilient.

The use of five basket arms in conjunction with a high-torque cathetershaft achieves a basket which can readily be controlled and orientedwithin the heart chamber.

The use of the semi-circular cross-section for the spine further allowsthe spines to fill the outwardly facing portion of the arm tubing, thusleaving the inwardly facing portion for the lead wires. Lead wires canthus extend through the tubing, and after being wrapped around thetubing can terminate at locations along the inwardly facing side of thearms away from the heart wall. Each exit hole and terminus can becovered and secured by adhesive. Only the outwardly facing portions ofthe lead wire which is wrapped around the tubing need be scraped bare toform the electrode.

The electrodes can thus be made quite small and are readilydistinguished fluoroscopically from the platinum ring markers. The ringmarkers readily identify each arm of the basket, as they are arranged ina staggered or spiral form on the different arms.

The basket which is formed as described is not only laterally stiff, butis also quite resilient and can form itself readily to the contour ofthe heart chamber, by pushing the inner catheter forward after thebasket has been exposed to the heart chamber through the withdrawal ofthe outer catheter. This helps ensure that all electrodes make goodcontact with the endocardial surface and provide strong electricalrecording signals.

The invention has been described in its preferred embodiment. Numerousvariations of the invention will be evident to those of ordinary skillin the art. The appended claims not only cover the preferred embodiment,but also such variations.

What is claimed is:
 1. A catheter for cardiac mapping comprising:(a) anelongated outer catheter tube; (b) an elongated inner catheter disposedwithin the outer catheter tube, said inner catheter comprising:(i) atubular catheter shaft having a proximal end and a distal end and acentral lumen; (ii) a plurality of flexible arms having distal andproximal ends said arms being connected at their proximal ends to thedistal end of the catheter shaft, each arm carrying at least oneelectrode and wherein each arm comprises a reinforcing spine, anelectrode lead wire electrically connected to each electrode carried onthe arm and a tubular sheath surrounding the reinforcing spine and leadwires; (iii) a proximal fitting rigidly fixing the proximal ends of thearms together, the proximal fitting being fixed to the distal end of thecatheter shaft and comprising a central aperture through which the leadwires extend; and (iv) a distal fitting fixing the distal ends of thearms together, (c) wherein the inner catheter is movable longitudinallywithin the outer catheter tube between a retracted position wherein thearms are disposed within the outer catheter tube and an extendedposition wherein the arms extend out of the distal end of the outercatheter tube and wherein the arms, in the extended position, bowoutwardly to form a predetermined basket shape.
 2. The catheter of claim1 wherein the lead wires comprise an insulated coating and theelectrodes are formed by passing end segments of the lead wires throughthe sheath, winding the end segments around the sheath and thenstripping the insulated coating off at least a portion of the lead wireend segment wound around the sheath.
 3. The catheter of claim 1 whereinthe proximal and distal fittings each comprise a polygonal segmenthaving a cross section in the shape of a polygon, the number of sides ofthe polygonal segment corresponding to the number of arms, and whereineach of the reinforcing spines of the arms has a proximal end whichcomprises a flat surface which engages a side of the polygonal segmentof the proximal fitting, and a distal end of the spine comprises a flatsurface which engages a flat surface of the polygonal segment of thedistal fitting, and wherein the proximal and distal fittings eachfurther comprise means for securing the ends of the spines of the armsto the polygonal segment.
 4. The catheter of claim 3 wherein the meansfor securing the spines to the polygonal segments comprises a retainingring which fits tightly around the spines, thereby holding the spinesagainst the sides of the polygonal segment.
 5. The catheter of claim 1wherein there are five arms.
 6. The catheter of claim 1 wherein thepredetermined basket shape has a central axis, and each of the spineshas a semi-circular transverse cross section with a flat side, the flatside of the spines facing toward the central axis.
 7. The catheter ofclaim 6 wherein each spine of an arm is disposed in a portion of thesheath of that arm remote from the central axis of the basket and theelectrode lead wires of that arm are disposed in the portion of thesheath of that arm nearer the central axis.
 8. The catheter of claim 1wherein the spines are made of NITINOL.
 9. A catheter for cardiacmapping comprising:(a) an elongated outer catheter tube; (b) anelongated inner catheter disposed in the outer catheter tube andafforded longitudinal movement therein between retracted and extendedpositions, said inner catheter comprising:(i) a catheter body having aproximal end and a distal end; (ii) a plurality of flexible armsextending from the distal end of the catheter body, each arm having adistal end and a proximal end; and (iii) means for fixing the distalends of the arms together, (iv) wherein the arms bow outwardly betweentheir proximal and distal ends and form a three-dimensional,predetermined shape with a central axis, the arms each comprising atubular sheath, a plurality of electrode lead wires and a reinforcingspine extending within the sheath, and a plurality of electrodeselectrically connected to the electrode lead wires at distal ends of thelead wires, the electrodes being disposed along the length of thesheath, said reinforcing spine comprising a semi-circular transversecross-sectional shape having a flat side, with the flat side facingtoward the central axis.
 10. The catheter of claim 9 wherein the spinesare made of NITINOL.
 11. The catheter of claim 9 wherein the lead wireshave an insulation coating and the electrodes are unitarily formed withthe lead wires by passing the distal ends of the lead wires through thesheath, winding the distal ends around the sheath, and then strippingthe insulation coating off at least a portion of the lead wire distalends which are wound around the sheath.
 12. The catheter of claim 9wherein each arm has a marker disposed on the sheath at a predeterminedposition with respect to each other marker, each marker being staggeredwith respect to the predetermined position of each marker on each othersheath.
 13. The catheter of claim 9 further comprising means for fixingthe proximal ends of the arms together.
 14. A catheter for cardiacmapping comprising:(a) a catheter body having a proximal end and adistal end; (b) a plurality of arms extending from the distal end of thecatheter body, each arm having a distal end and a proximal end; and (c)means for fixing the distal ends of the arms together,wherein the armsbow outwardly between their proximal and distal ends and form athree-dimensional, predetermined shape with a central axis, each armcomprising a flexible tubular sheath, a plurality of electrode leadwires having an insulated coating and a reinforcing spine extendingwithin the sheath, wherein an end portion of each electrode lead wirepasses through the sheath at spaced intervals, is wound around thesheath and then stripped of its insulated coating to form a plurality ofelectrodes at spaced intervals along the length of the sheath, andwherein the electrode lead wires pass through the sheath at positionsfacing the central axis of the predetermined three-dimensional shape andare wound around the sheath such that a distal end of the end portion ofeach of the wires lies at a position facing the central axis.
 15. Thecatheter of claim 14 further comprising a marker disposed along thelength of each arm which is made of a material more prominent underx-ray than a material forming the electrodes, the marker on each armbeing disposed in staggered relation with respect to each other marker.16. The catheter of claim 15 wherein the markers comprise platinum, andthe wires comprise MONEL.
 17. An electrophysiological mapping devicecomprising:an elongated tubular outer catheter having a distal end; anelongated tubular inner catheter disposed within the outer catheter andslidable with respect thereto, the inner catheter having electrodes at adistal end thereof; and an electronic recorder electrically connected tothe electrodes for electrically recording electric signals received bythe electrodes,wherein the distal end of the inner catheter isextendable from and retractable into the distal end of the outercatheter, and wherein the inner catheter comprises: (a) a tubularcatheter body having a proximal end and a distal end; (b) a plurality offlexible arms extending from the distal end of the catheter body, eacharm having a distal end and a proximal end and comprising a flexibletubular sheath and a reinforcing spine having a semi-circular crosssection extending within the sheath, each reinforcing spine having aproximal and a distal end, and wherein a plurality of electrodes aredisposed along the length of the sheath; (c) a first polygonal fittingfixing the proximal ends of the reinforcing spines together, the firstfitting being fixed to the distal end of the catheter body; and (d) asecond fitting fixing the distal ends of the reinforcing spinestogether,wherein, when the distal end of the inner catheter is extendedfrom the distal end of the outer catheter, the arms bow outwardly andform a three-dimensional, predetermined basket shape; and wherein theelectrodes are electrically connected to the recorder by insulated leadwires which extend from the recorder through the inner catheter body andsheaths of the arms to the electrodes.
 18. The mapping device of claim17 wherein each electrode is formed by an end segment of a lead wirewhich is passed through and wound around the sheath of an arm and then aportion of the wound segment is stripped of its insulation.
 19. Themapping device of claim 17 wherein the first and second fittings eachcomprise a fitting member having a cross section in the shape of apolygon, the number of sides of the polygon corresponding to the numberof spines, and wherein the proximal ends of the spines engage separatesides of the fitting member of the first fitting and the distal ends ofthe spines engage separate sides of the fitting member of the secondfitting, and the first and second fitting member each further comprisingmeans for securing the spines to the fitting member.
 20. The mappingdevice of claim 17 wherein each arm has a marker disposed thereon whichis made of a material more prominent under x-ray a material formingelectrodes, the marker on each arm being disposed in staggered relationwith respect to each other marker.
 21. The catheter of claim 20 whereinthe spines comprise NITINOL.